Conventional lever-activated amalgam carriers are well known and popular devices for filling dental cavities with amalgam or other materials. These devices typically include a hollow cylinder or sleeve into which the filling material is loaded, a plunger that is used to push out the material, and a lever which controls the movement of the plunger in the sleeve. U.S. Pat. No. 1,797,866 of C. S. Ivory is an early example of such an amalgam carrier. The construction and operation of amalgam carriers are well-known, and various modification of the basic construction described above have been developed. See, for example, the above-cited Ivory patent and U.S. Pat. Nos. 4,306,863, 4,355,976, and 4,273,543, the contents of which are incorporated by reference.
One problem that has confronted the art is the deterioration of the movable sleeve with use. Especially when amalgam filling materials are used, the interior of the sleeve becomes scratched and pitted. This increases the chances for contamination and also interferes with the smooth operation of the device. With current designs, the entire instrument must be disassembled in order to replace the sleeve, which is a time-consuming and delicate task.
Recently, dentists have been increasingly using dental composite resins for fillings and other restorative procedures. These materials are malleable when first dispensed for their intended use. One popular type of dental composite hardens by exposing the material to light, typically of a particular wavelength and intensity, to initiate polymerization. Other composite materials harden when the mixing of multiple components initiates polymerization.
A popular device among dentists for applying these materials is the system made popular by Dr. William Dragon and Centrix, Inc. An example of this is shown in U.S. Pat. No. 4,619,613. In this system, dental composite materials are loaded into cartridges by dental office personnel, or they may be preloaded into cartridges by dental manufacturers. These cartridges are then loaded into a syringe or gun-type apparatus for extruding the material into the oral cavity. This system is best used with materials having adequate flow characteristics to allow the extrusion of the composite material.
Recently, so-called "packable" composite dental filling materials have been developed. These materials are very hard and dense, and they have poor flow characteristics in the unpolymerized state. These packable composites are physically approaching the feel, handling, and packability of traditional dental amalgams, and as a result, lever-type amalgam carriers have become popular instruments for handling and conveying these composite resin materials. The present invention addresses the specific requirements of these packable composite materials and the need for a carrier designed to accommodate the special packaging and clinical handling of packable dental composite resins.